docs: def read_float_matrix(rx_specifier):
          """ Return float matrix as np array for the given rx specifier. """
  
          path, offset = rx_specifier.strip().split(':', maxsplit=1)
          offset = int(offset)
          sample_format = 4
  
          with open(path, 'rb') as f:
              # move to offset
              f.seek(offset)
  
              # assert binary ark
              binary = f.read(2)
              assert (binary == b'\x00B')
  
              # assert type float 32
              format = f.read(3)
              assert (format == b'FM ')
  
              # get number of mfcc features
              f.read(1)
              num_frames = struct.unpack('<i', f.read(4))[0]
  
              # get size of mfcc features
              f.read(1)
              feature_size = struct.unpack('<i', f.read(4))[0]
  
              # read feature data
              data = f.read(num_frames * feature_size * sample_format)
  
              feature_vector = np.frombuffer(data, dtype='float32')
              feature_matrix = np.reshape(feature_vector, (num_frames, feature_size))
  
              return feature_matrix